datasette/docs/_templates/sidebar/navigation.html

<div class="sidebar-tree">
  <ul>
    <li class="toctree-l1"><a class="reference internal" href="{{ pathto(master_doc) }}">Contents</a></li>
  </ul>
  {{ toctree(
    collapse=True,
    titles_only=False,
    maxdepth=3,
    includehidden=True,
) }}
</div>